Ask Allysha Almada why she supports Bernie Sanders, and Almada, a Glendora nurse who tried to form a union and was later fired, shoots right back with her own question: How could she not?

Sanders, the Vermont senator, doesn’t hedge with labor. Just about anything on the broader labor agenda, he champions. He recently unveiled legislation that read like a union wish list in front of a spirited throng of laborers shouting approval, Almada among them.

Sanders bristled when a reporter asked whether the bill would help him win endorsements from national unions – which it hasn’t. “It’s not a question of winning,” he snapped. “This is legislation I have supported, quite honestly, since literally the first year I was in Congress.” That was a quarter-century ago.

Despite Sanders’ deep support for labor, the national nurses’ organization that Almada sought to join is the only major union to endorse Sanders in the race for the Democratic nomination for president. It is dwarfed by much larger labor groups that are lining up with his arguably less committed, less reliable rival, Hillary Rodham Clinton.

National unions representing more than half of America’s 14.6 million unionized workers are already in Clinton’s corner, and many of the rest are heading in that direction. It is creating significant tension in some of the organizations and raising the question of whether the Sanders campaign is faltering or if union leadership has lost touch with its rank and file, large numbers of whom are turning out to support Sanders with unrivaled enthusiasm.

“There is no incentive for elected officials to support working-class values if union leaders are going to then say, ‘We need someone more conservative because they will win,’” said Larry Cohen, a former president of the Communication Workers of America who is advising Sanders. “That is what we are getting here. … Secretary Clinton is fine. But she is a corporate Democrat. That hasn’t worked.”

About 80,000 union members have enlisted in the Labor for Bernie campaign, through which they are pressuring the heads of their various unions not to endorse Clinton. They launch social media campaigns denouncing their union leadership when they are ignored. Local chapters of unions in key early states have gone rogue and thrown their support behind Sanders. Many of them parrot Sanders’ call for massive change — the kind union leaders have been demanding for decades — and they are resentful that their organizations would back the establishment at a time the insurgency finally has so much momentum.

Even so, the next major union poised to make an endorsement — the Service Employees International Union, which represents 2 million workers — is expected to throw its support behind Clinton. Union officials say their internal polling shows 75% of their members favor her. Sanders supporters may be louder, and may be concentrated in early-voting states getting a lot of attention, SEIU officials say, but Clinton is the candidate most of the union finds appealing.

“It’s a classic tension between the head and the heart,” said Lance Compa, who teaches labor law at the Cornell University School of Labor and Industrial Relations. Union leaders are feeling particularly risk-averse this election, with a hostile Congress and a Supreme Court that has labor in its crosshairs. The court will be hearing a case against the California Teachers Assn. that poses an existential threat to public employee unions nationwide, with justices weighing whether to ban them from requiring the employees they represent to pay dues. Labor leaders are horror-struck by the prospect of a Republican president filling the next Supreme Court vacancy.

“Union leaders are negotiators by nature,” Compa said. “They understand you can’t get everything they want. You get the best deal in the end. That is what they are looking at now” as they weigh whom to endorse.

As the endorsements stack up in Clinton’s favor, they are consistently accompanied by statements from union leaders pointing to her winnability. Lee Saunders, president of the 1.6-million-strong American Federation of State, County and Municipal Employees, said a factor in Clinton winning its support a couple of weeks ago was that she “will be able to deliver a victory.”

But getting to those endorsements has, indeed, resembled a workplace negotiation, with Sanders playing the role of bargaining chip. Union leaders began in the spring by scoffing at the suggestion they would line up in Clinton’s corner. They took aim at ground they lost during the Obama administration, bemoaned their disappointment with "Wall Street Democrats," vowed that nobody would be getting their support without being very specific about what they would do for the cause.

Sanders eagerly obliged. He promised to push a $15 minimum wage, to resist international trade agreements reviled by labor, to break up the big banks with a revival of the Glass-Steagall Act. The AFL-CIO praised the legislation he introduced last month — with Almada at his side — to replace secret balloting with a system in which workers trying to organize need only get a majority of colleagues to sign cards. The Teamsters expressed delight with his legislation to protect worker pensions.

Clinton swiftly began moving in the same direction. Just not as far. But far enough for many.

“Yes, Bernie Sanders is 100% with labor,” said Compa. “But Hillary is 90%. Then you take all the other things into account, and it is better than half a loaf for many of these unions.”

Bernie Sanders, the insurgent candidate for president, says he plans to give "a major speech" soon explaining what he means when he calls himself a democratic socialist.

"I think there are a lot of people who, when they hear the word 'socialist,' get very, very nervous," Sanders told reporters...

Bernie Sanders, the insurgent candidate for president, says he plans to give "a major speech" soon explaining what he means when he calls himself a democratic socialist.

"I think there are a lot of people who, when they hear the word 'socialist,' get very, very nervous," Sanders told reporters...

(Doyle McManus)

Such reasoning exasperates Kenneth Zinn, political director of National Nurses United, the union that endorsed Sanders.

“This is about building a massive movement that can propel massive change,” he said in an interview. “There is a presumption, and frankly an arrogance, that someone can or can’t get support. Bernie Sanders just raised over $25 million from small donors. You can’t do that if you don’t have massive support.”

Zinn was sitting next to Almada, who was in Washington to talk about getting fired from the hospital where she was born and her mother has worked for 30 years. “Americans would be horrified if they saw what companies could get away with in terms of harassing or intimidating workers,” she said of her experience trying to organize co-workers.

Almada was invited to share her story at a White House labor issues forum, at the Sanders rally and at a small event with the nation’s most powerful labor leader, AFL-CIO President Richard Trumka. He thanked Almada for her courage, as he has many Sanders enthusiasts from the rank and file who are pushing to insert labor’s agenda into the presidential election.

But few are betting the AFL-CIO is going to endorse the Vermonter.

Sanders is not the first labor absolutist to confront this kind of betrayal. Other similarly positioned Democrats have been through it, including former presidential candidates Tom Harkin and Dick Gephardt. Ironically, it is now Harkin, a former Iowa senator now supporting Clinton, who is trying to rally laborers for the establishment candidate. He took a swipe at Sanders this week during an interview on Boston radio, heard in New Hampshire, where Democrats are threatening to disrupt Clinton’s march to the nomination by voting for Sanders.

“Bernie Sanders has been in public office longer than Hillary Clinton,” Harkin said. “What makes him not establishment?”